1. Field of the Invention
The present invention relates generally to a gas turbine engine and, more particularly, to a hybrid shape spinner nose configuration in a gas turbine engine having a bypass duct.
2. Description of the Prior Art
A gas turbine engine of the turbofan type generally includes a forward fan and booster compressor, a middle core engine, and an aft low pressure power turbine. The core engine encompasses a compressor, a combustor and a high pressure turbine in a serial flow relationship. The compressor and high pressure turbine of the core engine are interconnected by a central shaft. The compressor is rotatably driven to compress air entering the core engine to a relatively high pressure. This high pressure air is then mixed with fuel in the combustor and ignited to form a high energy gas stream. This gas stream flows aft and passes through the high pressure turbine, rotatably driving it and the core engine shaft which, in turn, rotatably drives the compressor.
In the turbofan engine, the residual gas stream leaving the core engine high pressure turbine is expanded through a second turbine, which as mentioned above is the aft low pressure turbine. The aft low pressure turbine, in turn, drives the forward fan via a separate shaft which extends forwardly through the central shaft of the high pressure turbine rotor. Although some thrust is produced by the residual gas stream exiting the core engine, most of the thrust is produced by an air stream generated by the forward fan that bypasses the core engine through an annular duct disposed radially outwardly of and surrounding the core engine.
The annular bypass duct is located rearward of a row of circumferentially spaced fan blades of the forward fan and between the outer annular nacelle and inner splitter fairing of the engine. Typically, the turbofan engine also includes a spinner nose projecting forwardly from the row of fan blades. Both the spinner nose and row of fan blades are a rotor of the booster compressor.
The rotary energy of the core engine thus produces thrust indirectly by driving the forward fan. Ensuring uninterrupted operation of the core engine is thereby essential to generation of thrust by the forward fan. One condition which can be detrimental to core engine operation is ingestion of ice, hail and miscellaneous debris into the core engine inwardly of the splitter fairing rather than diversion of such foreign materials outwardly of the splitter fairing through the bypass duct.
Ice formation typically tends to occur on the spinner nose of the engine. The spinner nose has different shapes in different engines. Typically, the configuration of the spinner nose is either elliptical or conical with each having both advantages and disadvantages. The elliptical shaped spinner nose tends to shed or rebound debris outwardly of the core engine and into the engine's bypass duct, thus providing the engine core with a level of protection against entry of ice, hail and miscellaneous ground debris. However, cold temperature testing has demonstrated that the conical shaped spinner nose will build up less ice in the first place than an elliptical spinner nose for the same operating conditions and environment. However, the conical shaped spinner nose produces little or no outward rebound debris and thus can permit up to 100% capture of debris rearwardly up the spinner nose surface and into the core engine.
The degree to which ice, hail and debris will be ingested into the core engine past the splitter fairing also depends upon other factors besides the shape of the spinner nose. These factors are the size of the gap between the rear radial edge of the fan blades and the leading edge of the splitter fairing and the axial depth of the fan blades.
Consequently, a need exists for improvement of the design of the spinner nose configuration which will reduce the degree to which ice, hail and debris is ingested into the core engine.